Semiconductors are widely used for integrated circuits for electronic applications, including computers, radios, and televisions, as examples. Such integrated circuits typically use multiple transistors fabricated in single crystal silicon. It is common for there to be millions of semiconductor devices on a single semiconductor product. To provide the necessary signal and power interconnections for the multiplicity of semiconductor devices, many integrated circuits now include multiple levels of metallization.
The semiconductor industry continuously strives to decrease the size of the semiconductor devices located on integrated circuits. Miniaturization is generally needed to accommodate the increasing density of the circuits necessary for today's advanced semiconductor products. One of the areas where miniaturization is needed is in forming the contacts between conductors in an integrated circuit.
In the present technology, contact holes are made in a dielectric that overlies the semiconductor substrate. These contact holes are made using a photolithographic process. For example, after the transistors are formed, a pre-metal dielectric (PMD) is deposited over the substrate. An antireflective coating (ARC) can then be deposited over the pre-metal dielectric and a photoresist applied. Radiation is directed toward the photoresist through a mask so that selected portions of the photoresist are irradiated. Portions of the resist, and underlying ARC, can then be removed to expose portions of the interlevel dielectric. These portions can be anisotropically etched to create the contact holes.
The contact holes are filled with a conductor to create a plug. For example, a liner such as titanium followed by titanium nitride is formed along sidewalls of the contact hole. The hole can then be filled with a conductor such as tungsten. The tungsten can then be removed to the level of the pre-metal dielectric using a chemical mechanical polish or etch back process.